PDF Shop Manual KOMATSU PC228US-3E0 PC228USLC-3E0 Hydraulic Excavator - 4 MB

This comprehensive shop manual is for the Komatsu PC228US-3E0 and PC228USLC-3E0 hydraulic excavators.

It contains detailed service and repair information used by professional technicians.

The manual covers everything from the engine and hydraulics to the electrical system, with step-by-step instructions and specifications.

This is the ultimate resource for keeping your Komatsu excavator in top working order.

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--- Page 1 ---
SEN01418-10


HYDRAULIC   PC228US   -3E0
EXCAVATOR
            PC228USLC -3E0
                             PC228US- 40001
            SERIAL NUMBERS                      and up
                             PC228USLC- 40001

--- Page 3 ---
SEN01420-10                                                                                                      00 Index and foreword


         Disassembly and assembly of final drive assembly.................................................................         3
         Removal and installation of swing machinery assembly.......................................................... 11
         Disassembly and assembly of swing machinery assembly ..................................................... 13
         Removal and installation of swing circle assembly .................................................................. 21
     Undercarriage and frame                                                                                      SEN01926-02
         Disassembly and assembly of track roller assembly ...............................................................         2
         Disassembly and assembly of idler assembly .........................................................................      3
         Disassembly and assembly of recoil spring.............................................................................    6
         Expansion and installation of track shoe assembly .................................................................       8
         Removal and installation of revolving frame ............................................................................ 10
         Removal and installation of counterweight assembly .............................................................. 12
         Removal and installation of maintenance counterweight (at rear of engine) ........................... 13
         Removal and installation of maintenance counterweight assembly (above pump) ................. 14
     Hydraulic system                                                                                             SEN01927-02
         Removal and installation of center swivel joint assembly ........................................................         2
         Disassembly and assembly of center swivel joint....................................................................       4
         Removal and installation of hydraulic tank assembly ..............................................................        5
         Removal and installation of work equipment pump .................................................................         7
         Removal and installation of control valve assembly ................................................................ 11
         Disassembly and assembly of control valve assembly............................................................ 13
         Disassembly and assembly of work equipment PPC valve assembly..................................... 15
         Disassembly and assembly of travel PPC valve assembly ..................................................... 17
         Disassembly and assembly of hydraulic cylinder assembly .................................................... 20
     Work equipment                                                                                               SEN01928-01
         Removal and installation of work equipment assembly ...........................................................           2
     Cab and its attachments                                                                                      SEN01929-01
         Removal and installation of operator’s cab assembly..............................................................         2
         Removal and installation of operator’s cab glass (Stuck glass)...............................................             4
         Removal and installation of front window assembly ................................................................ 13
         Removal and installation of floor frame assembly ................................................................... 14
     Electrical system                                                                                            SEN01930-01
         Removal and installation of air conditioner compressor assembly ..........................................                2
         Removal and installation of air conditioner condenser assembly ............................................               4
         Removal and installation of air conditioner unit assembly .......................................................         5
         Removal and installation of machine monitor assembly ..........................................................           7
         Removal and installation of pump controller assembly............................................................          8
         Removal and installation of engine controller assembly ..........................................................         9
         Removal and installation of KOMTRAX communication modem assembly ............................ 11

 90 Diagrams and drawings
    Hydraulic diagrams and drawings                                                                                          SEN01439-01
        Hydraulic circuit diagram .........................................................................................................  3
    Electrical diagrams and drawings                                                                                         SEN01440-02
        Electrical circuit diagram.......................................................................................................... 3
        Connector list and stereogram................................................................................................. 17


10                                                                                                                 PC228US, USLC-3E0

--- Page 4 ---
SEN01421-02                                                                           00 Index and foreword


3.   Filing method
     File by the brochures in the correct order of the form number printed in the shop manual composition
     table.

     q   Revised edition mark
         When a manual is revised, the ones and tens digits of the form number of each brochure is
         increased by 1. (Example: 00, 01, 02 …)

     q   Revisions
         Revised brochures are shown in the shop manual composition table.

4.   Symbols
     Important safety and quality portions are marked with the following symbols so that the shop manual will
     be used practically.

         Symbol            Item                                      Remarks

           k              Safety      Special safety precautions are necessary when performing work.

                                      Special technical precautions or other precautions for preserving stan-
           a             Caution
                                      dards are necessary when performing work.

         4
                                      Weight of parts of component or parts. Caution necessary when
                         Weight
                                      selecting hoisting wire, or when working posture is important, etc.

         3
                        Tightening    Places that require special attention for tightening torque during
                          torque      assembly.

         2                Coat        Places to be coated with adhesives, etc. during assembly.


          5
                       Oil, coolant   Places where oil, etc. must be added, and capacity.


          6
                          Drain       Places where oil, etc. must be drained, and quantity to be drained.


5.   Units
     In this shop manual, the units are indicated with International System of units (SI). For reference, con-
     ventionally used Gravitational System of units is indicated in parentheses { }.


8                                                                                       PC228US, USLC-3E0

--- Page 5 ---
SEN01421-02                                                                        00 Index and foreword


Points to remember when handling hydraulic equipment
With the increase in pressure and precision of hydraulic equipment, the most common cause of failure is dirt
(foreign material) in the hydraulic circuit. When adding hydraulic oil, or when disassembling or assembling
hydraulic equipment, it is necessary to be particularly careful.


1.   Be careful of the operating environment.
     Avoid adding hydraulic oil, replacing filters, or
     repairing the machine in rain or high winds, or
     places where there is a lot of dust.

2.   Disassembly and maintenance work in the
     field
     If disassembly or maintenance work is carried
     out on hydraulic equipment in the field, there is
     danger of dust entering the equipment. It is
     also difficult to check the performance after
     repairs, so it is desirable to use unit exchange.
     Disassembly and maintenance of hydraulic
     equipment should be carried out in a specially
     prepared dustproof workshop, and the perfor-
     mance should be checked with special test
     equipment.

3.   Sealing openings
     After any piping or equipment is removed, the
     openings should be sealed with caps, tapes, or
     vinyl bags to prevent any dirt or dust from
     entering. If the opening is left open or is
     blocked with a rag, there is danger of dirt
     entering or of the surrounding area being
     made dirty by leaking oil so never do this. Do
     not simply drain oil out onto the ground, but
     collect it and ask the customer to dispose of it,
     or take it back with you for disposal.

4.   Do not let any dirt or dust get in during
     refilling operations
     Be careful not to let any dirt or dust get in when
     refilling with hydraulic oil. Always keep the oil
     filler and the area around it clean, and also use
     clean pumps and oil containers. If an oil clean-
     ing device is used, it is possible to filter out the
     dirt that has collected during storage, so this is
     an even more effective method.


18                                                                                   PC228US, USLC-3E0

--- Page 6 ---
SEN01421-02                                                                         00 Index and foreword


     4)   Checking muffler and exhaust pipe for damage and looseness
          1] Visually check the muffler, exhaust pipe and their mounting parts for a crack and damage.
               If any part is damaged, replace it.
          2] Check the mounting bolts and nuts of the muffler, exhaust pipe and their mounting parts for
               looseness.
               If any bolt or nut is loosened, retighten it.
     5)   Checking muffler function
          Check the muffler for abnormal sound and sound different from that of a new muffler.
          If any abnormal sound is heard, repair the muffler, referring to “Troubleshooting” and “Disassembly
          and assembly”.


28                                                                                    PC228US, USLC-3E0

--- Page 7 ---
SEN01421-02                                                                       00 Index and foreword


Liters to U.K. Gallons
                                                                         1 l = 0.21997 U.K.Gal
            0       1        2        3        4        5         6      7        8       9
  0         0     0.220    0.440    0.660    0.880    1.100     1.320  1.540    1.760   1.980
  10      2.200   2.420    2.640    2.860    3.080    3.300     3.520  3.740    3.950   4.179
  20      4.399   4.619    4.839    5.059    5.279    5.499     5.719  5.939    6.159   6.379
  30      6.599   6.819    7.039    7.259    7.479    7.699     7.919  8.139    8.359   8.579
  40      8.799   9.019    9.239    9.459    9.679    9.899    10.119 10.339 10.559 10.778

  50     10.998   11.281   11.438   11.658   11.878   12.098   12.318   12.528   12.758   12.978
  60     13.198   13.418   13.638   13.858   14.078   14.298   14.518   14.738   14.958   15.178
  70     15.398   15.618   15.838   16.058   16.278   16.498   16.718   16.938   17.158   17.378
  80     17.598   17.818   18.037   18.257   18.477   18.697   18.917   19.137   19.357   19.577
  90     19.797   20.017   20.237   20.457   20.677   20.897   21.117   21.337   21.557   21.777


kgm to ft.lb
                                                                              1 kgm = 7.233 ft.lb
            0       1        2        3        4        5        6        7        8       9
  0         0       7.2     14.5     21.7     28.9     36.2     43.4     50.6     57.9    65.1
  10       72.3    79.6     86.8     94.0    101.3    108.5    115.7    123.0    130.2   137.4
  20      144.7   151.9    159.1    166.4    173.6    180.8    188.1    195.3    202.5   209.8
  30      217.0   224.2    231.5    238.7    245.9    253.2    260.4    267.6    274.9   282.1
  40      289.3   296.6    303.8    311.0    318.3    325.5    332.7    340.0    347.2   354.4

  50      361.7   368.9    376.1    383.4    390.6    397.8    405.1    412.3    419.5    426.8
  60      434.0   441.2    448.5    455.7    462.9    470.2    477.4    484.6    491.8    499.1
  70      506.3   513.5    520.8    528.0    535.2    542.5    549.7    556.9    564.2    571.4
  80      578.6   585.9    593.1    600.3    607.6    614.8    622.0    629.3    636.5    643.7
  90      651.0   658.2    665.4    672.7    679.9    687.1    694.4    701.6    708.8    716.1

  100     723.3  730.5  737.8 745.0   752.2  759.5 766.7   773.9  781.2  788.4
  110     795.6  802.9  810.1 817.3   824.6  831.8 839.0   846.3  853.5  860.7
  120     868.0  875.2  882.4 889.7   896.9  904.1  911.4  918.6  925.8  933.1
  130     940.3  947.5  954.8 962.0   969.2  976.5 983.7   990.9  998.2 1005.4
  140    1012.6 1019.9 1027.1 1034.3 1041.5 1048.8 1056.0 1063.2 1070.5 1077.7

  150    1084.9   1092.2   1099.4   1106.6   1113.9   1121.1   1128.3   1135.6   1142.8   1150.0
  160    1157.3   1164.5   1171.7   1179.0   1186.2   1193.4   1200.7   1207.9   1215.1   1222.4
  170    1129.6   1236.8   1244.1   1251.3   1258.5   1265.8   1273.0   1280.1   1287.5   1294.7
  180    1301.9   1309.2   1316.4   1323.6   1330.9   1338.1   1345.3   1352.6   1359.8   1367.0
  190    1374.3   1381.5   1388.7   1396.0   1403.2   1410.4   1417.7   1424.9   1432.1   1439.4


38                                                                                 PC228US, USLC-3E0

--- Page 8 ---
SEN01423-01                                                                                     01 Specification


Weight table                                               1
k This weight table is prepared for your reference when handling or transporting the components.


                                                                                                            Unit: kg
                       Machine model                               PC228US-3E0              PC228USLC-3E0
                        Serial number                                            40001 and up
Engine assembly                                                        735                        735
• Engine                                                               575                        575
• Damper                                                                6                          6
• Hydraulic pump                                                       154                        154
Radiator and oil cooler assembly                                       126                        126
Hydraulic tank and filter assembly (Not including hydraulic oil)       146                        146
Fuel tank assembly (Not including fuel)                                131                        131
Revolving frame                                                       1,854                      1,854
Cab                                                                    251                        251
Operator’s seat                                                         27                         27
Counterweight                                                         6,060                      6,060
Swing machinery                                                        224                        224
Control valve                                                          280                        280
Swing motor                                                            51.5                       51.5
Travel motor                                                          98 x 2                     98 x 2
Center swivel joint                                                    30.3                       30.3
Track frame assembly (Not including piping)                           4,269                      4,797
• Track frame                                                         2,260                      2,644
• Swing circle                                                         267                        267
• Idler                                                              101 x 2                    101 x 2
• Idler cushion                                                      118 x 2                    118 x 2
• Carrier roller                                                      14 x 4                     14 x 4
• Track roller                                                       36 x 14                    36 x 18
• Final drive (including travel motor)                               372 x 2                    372 x 2
Track shoe assembly
• Standard triple shoe (600 mm)                                      1,215 x 2                  1,395 x 2
• Standard triple shoe (700 mm)                                      1,405 x 2                  1,530 x 2
• Standard triple shoe (800 mm)                                      1,530 x 2                  1,670 x 2
• Flat shoe (600 mm)                                                 1,635 x 2                  1,780 x 2
• Swamp shoe (860 mm)                                                1,630 x 2                  1,775 x 2
• Road liner (Rubber pad type) (600 mm)                              1,470 x 2                  1,600 x 2


6                                                                                          PC228US, USLC-3E0

--- Page 9 ---
SEN01426-00                                   10 Structure, function and maintenance standard


Power train                                                                                1
Power train                               1


1.   PPC lock solenoid valve                   7. Final drive
2.   Travel speed switch solenoid valve        8. Travel motor (HMV110ADT-2)
3.   Swing brake solenoid valve                9. Hydraulic pump (HPV95+95)
4.   Idler                                     10. Engine (SAA6D107E-1)
5.   Center swivel joint                       11. Swing motor (KMF125ABE-6)
6.   Control valve                             12. Swing machinery
                                               13. Swing circle


2                                                                        PC228US, USLC-3E0

--- Page 10 ---
SEN01427-00       10 Structure, function and maintenance standard


Idler         1


4                                            PC228US, USLC-3E0

--- Page 11 ---
SEN01428-00


HYDRAULIC EXCAVATOR                                                        1SHOP MANUAL


PC228US-3E0
PC228USLC-3E0


Machine model                            Serial number
PC228US-3E0                               40001 and up
PC228USLC-3E0                             40001 and up


10 Structure, function and
   maintenance standard                                                                                                                                1
Hydraulic system, Part 1
Hydraulic system, Part 1 ................................................................................................................................. 2
      Hydraulic equipment layout drawing .................................................................................................... 2
      Hydraulic tank ...................................................................................................................................... 4
      Hydraulic pump .................................................................................................................................... 6


PC228US, USLC-3E0                                                                                                                                         1

--- Page 12 ---
SEN01428-00                                           10 Structure, function and maintenance standard


1. LS valve


PA : Pump port                                         1.   Sleeve
PDP : Drain port                                       2.   Piston
PLP : LS control pressure output port                  3.   Spool
PLS : LS pressure input port                           4.   Spring
PP : Pump port                                         5.   Sheet
PPL : Control pressure input port                      6.   Sleeve
PSIG : LS mode selector pilot port                     7.   Plug
                                                       8.   Locknut

Function
q  The LS (load sensing) valve detects the load
   and controls the delivery.
q  This valve controls main pump delivery (Q)
   according to differential pressure (dPLS)[= PP
   – PLS], called the LS differential pressure (the
   difference between main pump pressure (PP)
   and control valve outlet port pressure (PLS)).
q  Main pump pressure (PP), pressure (PLS)
   (called the LS pressure) coming from the con-
   trol valve output, and pressure (PSIG) (called
   the LS selector pressure) from the proportional
   solenoid valve enter this valve.
q  The relationship between the LS differential
   pressure between the main pump pressure
   (PP) and LS pressure (PLS) (dPLS) [= (PP) –
   (PLS)] and the pump delivery (Q) changes as
   shown in the diagram according to LS selector
   current (ISIG) of the LS-EPC valve.
q  If (ISIG) changes from 0 to 1A, setting force of
   the spring changes, too. As the result, the
   specified median of the pump delivery volume
   switching point changes as shown in the dia-
   gram. It will change in the range of 0.69 to 2.2
   MPa {in the range of 7.0 to 22.0 kg/cm2}.


12                                                                               PC228US, USLC-3E0

--- Page 13 ---
SEN01428-00                                              10 Structure, function and maintenance standard


q    The relationship between the average pump
     pressure (PP1 + PP2)/2 and servo piston (9) in
     terms of their positions can be represented by
     the broken line in the figure springs (4) and (6)
     form the double springs.
q    The relationship between the average pump
     pressure (PP1 + PP2)/2 and average pump
     delivery (Q) becomes as shown below.


q    If command voltage (X) sent to PC-EPC valve
     solenoid (1) increases further, the relationship
     between average pump pressure (PP1 + PP2)/
     2, and pump delivery (Q) is proportional to the
     force of the PC-EPC valve solenoid and moves
     in parallel.
q    Namely, the force of PC-EPC valve solenoid
     (1) is added to the pushing force to the right
     because of the pump pressure applied to the
     spool (3), so the relationship between the aver-
     age pump pressure (PP1 + PP2)/2 and the
     pump delivery (Q) moves from (A) to (B) as the
     command current (X) is increased.


22                                                                                  PC228US, USLC-3E0

--- Page 14 ---
SEN01429-01      10 Structure, function and maintenance standard


Sectional view
(1/5)


4                                           PC228US, USLC-3E0

--- Page 15 ---
SEN01429-01                                            10 Structure, function and maintenance standard


CLSS                                              1
Outline of CLSS


Features                                                Configuration
CLSS stands for Closed center Load Sensing Sys-         q  CLSS is configured with variable capacity pis-
tem, which has the following characteristics:              ton pumps, control valves, and respective
                                                           actuators.
q    Fine control not influenced by load                q  The hydraulic pump is configured with pump
q    Controllability enabling digging even with fine       body, PC valve and LS valve.
     control
q    Ease of compound operation ensured by flow
     divider function using area of opening of spool
     during compound operations
q    Energy saving using variable pump control


14                                                                                 PC228US, USLC-3E0

--- Page 16 ---
SEN01429-01                                             10 Structure, function and maintenance standard


Pressure compensation valve
1.   During independent operation and under maximum load pressure

(If the load pressure is higher than other work equipment during a combined operation)


1.   Hydraulic pump                                      4.   Piston
2.   Valve                                               5.   Spring
3.   Shuttle valve                                       6.   LS shuttle valve

Function                                                 q    As principle, port (C) and spring chamber (E)
q  Pressure compensation valve works as the                   are not interconnected in an integrated pres-
   load check valve.                                          sure compensation valve.
q  If the pump pressure (LS pressure) is lower           q    If high peak pressure is generated at port (C),
   than the load at port (c), shuttle valve (3) in            valve (7) does not collide with the valve cham-
   pressure compensation valve piston (4) inter-              ber.
   connects spring chamber (E) and port (C).             q    With a bucket valve, etc., port (C) and spring
q  The force of spring (5) operates piston (4) and            chamber (E) are designed to interconnect
   valve (2) to the closing direction.                        before valve (7) is seated.

Integrated pressure compensation valve
q   High stress may occur when valve (2) collides
    with valve chamber seat portion (C) if a high
    peak pressure is generated in the actuator cir-
    cuit or repetitive peak pressure occurs continu-
    ously (example: when using the breaker).
q   To prevent this, a pressure compensation
    valve with integrated valve (2) and piston (4) is
    used.
q   With the present machine, this device is
    adopted for the bucket valve (cylinder bottom)
    and the service valve.


24                                                                                    PC228US, USLC-3E0

--- Page 17 ---
SEN01429-01                                                10 Structure, function and maintenance standard


2.   When flows from the pumps are divided [if pilot pressure (PS) is ON]


Operation
q  Pilot pressure (PS) turns ON, and output pres-
   sure from the PPC valve shifts main spool (1)
   to the left, and ports (E) and (F) are divided.
q  Pressurized oil discharged from the two pumps
   are sent to respective control valves.

     P1 pressure: To bucket, L.H. travel, and boom
     P2 pressure: To swing, R.H. travel, and arm

q    LS spool (3) too shifts to the left under the out-
     put pressure from the PPC valve, intercon-
     nects ports (A) and (C) and divides other ports.
q    Forwards LS pressure led from each control
     valve spool to LS circuits (5), (6), (7) and (8) to
     respective control valves.


34                                                                                    PC228US, USLC-3E0

--- Page 18 ---
SEN01429-01                                              10 Structure, function and maintenance standard


2.   When the boom is in neutral


Operation
q  Moves the lever to neutral with the boom
   raised.
q  Pressurized oil flown inside poppet (5) from
   orifice (a) of poppet (5) is closed by pilot piston
   (2).
q  The holding pressure of boom cylinder bottom
   works on the ring-shaped area (S) caused by
   the difference between outside diameter (d1)
   of poppet (5) and seat diameter (d2) to move it
   to the right.
q  The sum of this force and the force of spring
   (4) closes poppet (5).
q  Pressurized oil from the control valve and the
   holding pressure of the boom cylinder bottom
   are shut off.


44                                                                                  PC228US, USLC-3E0

--- Page 19 ---
SEN01429-01                                              10 Structure, function and maintenance standard


Variable pressure compensation valve
(Installed to the service valve)


A.   Pump discharge pressure (P) (From service
     valve spool)
B.   Cylinder port
C.   Load pressure of other work equipment

1.   Valve
2.   Spring
3.   Sleeve
4.   Poppet
5.   Spring
6.   Screw
7.   Locknut
8.   Cap

Function
q  Regulates flow distribution to the service valve
   when the service valve (attachment) and the
   work equipment valve (boom raising, etc.) are
   operated together. (Equivalent surface area
   ratio variable)
q  Pressurized oil from the service valve spool is
   applied to the left side of valve (1) and is led to
   chamber (g) via orifice (a).
q  LS pressure is led to chamber (e) via orifice
   (d).
q  Pressurized oil of cylinder port is led to cham-
   ber (h) via passage (c) and orifice (f).
q  The force of spring (2) acts on valve (1), and
   the force of spring (5) acts on poppet (4).
q  The force of spring (5) can be adjusted with
   screw (6).


54                                                                                  PC228US, USLC-3E0

--- Page 20 ---
SEN01429-01


PC228US, 228USLC-3E0 Hydraulic excavator
Form No. SEN01429-01


                                           © 2010 KOMATSU
                                           All Rights Reserved
                                           Printed in Japan 09-10


64

--- Page 21 ---
SEN01430-01   10 Structure, function and maintenance standard


10                                       PC228US, USLC-3E0

--- Page 22 ---
SEN01430-01                                         10 Structure, function and maintenance standard


Solenoid valve
PPC lock, 2-stage relief, swing brake, travel speed, travel junction, and merge-divider solenoid valves


1.   PPC lock solenoid valve                          8. Moving core
2.   2-stage relief solenoid valve                    9. Coil
3.   Travel speed solenoid valve                      10. Spool
4.   Swing brake solenoid valve                       11. Block
5.   Travel junction solenoid valve                   12. Spring
6.   Merge-divider solenoid valve
7.   Connector

20                                                                               PC228US, USLC-3E0

--- Page 23 ---
SEN01430-01                                             10 Structure, function and maintenance standard


Operation of parking brake

1) When starting travel


q    As the travel lever is operated, pressurized oil
     from the pump activates counterbalance valve
     spool (19), opening the parking brake circuit.
q    The pressurized oil is conducted to chamber
     (e) of brake piston (12) and compresses spring
     (11), pushing piston (12) toward left.
q    Since the pushing force to plate (13) and disc
     (14) disappears, plate (13) is separated from
     disc (14) and the brake is released.


30                                                                                 PC228US, USLC-3E0

--- Page 24 ---
SEN01430-01                10 Structure, function and maintenance standard


Reverse prevention valve


40                                                    PC228US, USLC-3E0

--- Page 25 ---
SEN01431-00                    10 Structure, function and maintenance standard


Dimensions of components   1
1.   Dimension of arm


4                                                         PC228US, USLC-3E0

--- Page 26 ---
10 Structure, function and maintenance standard                                               SEN01433-03


Operation of system                                1    Stopping engine
Starting engine                                         q   When detecting that the starting switch is set to
q   When the starting switch is turned to the               the “STOP” position, the engine controller cuts
    START position, the starting signal flows to the        the signal of the supply pump drive solenoid to
    starting motor. Then, the starting motor turns to       stop the engine.
    start the engine.

    When it happens, the engine controller checks
    the signal voltage from the fuel control dial and
    sets the engine speed to the speed set by the
    fuel control dial.


Engine speed control
q  The fuel control dial sends a signal voltage cor-
   responding to the rotation angle to the engine
   controller.

    The engine controller sends a driving signal to
    the supply pump depending on the signal volt-
    age to control the fuel injection pump, and
    eventually controls the engine speed.


PC228US, USLC-3E0                                                                                          3

--- Page 27 ---
10 Structure, function and maintenance standard   SEN01433-03


PC228US, USLC-3E0                                         13

--- Page 28 ---
10 Structure, function and maintenance standard       SEN01433-03


5.   Auto-warm-up and overheat prevention function


Function
q  The engine automatic warm-up function
   increases the engine speed to warm up the
   engine if coolant temperature is too low after
   the engine starts.
q  The overheat prevention function reduces the
   pump load when coolant or hydraulic oil tem-
   perature is too high during operation to protect
   the engine from overheating.


PC228US, USLC-3E0                                             23

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10 Structure, function and maintenance standard                                           SEN01433-03


2)   Oil pressure sensor


1.   Sensor
2.   Connector

Function                                              q   The relationship between the pressure applied
q  The pump pressure sensor is installed to the           to sensors (P) and output voltage (E) is shown
   input circuit of the control valve.                    in the figure below.

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